Convertible switch



SPt 10, 19.?9.v G. R. TowNsl-:ND 1,728,019

CONVERTIBLE SWITCH- F'iled July l, 1927 @-2- MllllllIl-lllllllllllmllll Milli ZZ- I Inventor:

George RTownsend kg His Attorne Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

l GEORGE R. TOWNSEND, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

CONVERTIBLE SWITCH.

Application led July 1, 1927. Serial No. 202,927.

The invention relates to electric switches, particularly switches operable between the circuit opening and the circuit closing positions and biased to one of these positions. The object of the invention is the provision of an improved formof switch which readily may be converted to either the normally open .or the normally closed type.

The improved form of switch of the present invention is particularly advantageous for use as a limit switch or a switch adapted to be operated upon movement of some object such as a door, lever, or the like. In such service it is sometimes desired that the switch be normally open and operable to close a circuit while in other cases it is desired that the switch be normally closed and operable to open a circuit in order to actuate a signal, alarm, or start or stop some electrical apparatus or perform some other similar function. With the improved form of switch of the present invention it is possible to convert the switch to either the normally open or the normally closed type so as to either close or open the control circuit of the signal or motor as may be desired upon operation of the switch.

The accompanying drawings illustrate a preferred form of enclosed type of limit switch embodying the improvements of the present invention. Fig. l is a perspective view of the enclosed limit switch; Fig. 2 is an enlarged view of the switch with the cover removed from the enclosing casing; Figs. 3 and 4 are sectional views of the switch showing the relation of the cooperating parts when the switch is arranged to be biased to the circuit opening position; while Figs. 5 and 6 show the relations of the cooperating parts when the switch is arranged to be biased tothef circuit closing position.

Fig. 1 shows the enclosing casing 10 for the switch provided with the removable cover plate 11 and also the conduit receiving opening 12 for the circuit connections con- .,trolled by the switch. It will be noted that the switch operating shaft 13 extends out-l side the casing 10 and the projecting end may be located either on the right or lefthand side of the casing. While not shown, both ends of the shaft 13 may project from the casing' if desired. A switch operating lever arm 14 carrying the roller 15 is arranged to be adjustably mounted upon the projecting end of the switch operating shaft 13 in any desired position by means of the lock nuts 16f As more clearly shown in the enlarged view of Fig. 2, the switch mechanism enclosed within the casing 10 comprises the movable bridging contacty 17 and the two cooperating stationary contacts 18. As may be seen from the sectional views of Figs. 3 to 6, the bridging contact 17 is loosely mounted at its middle on the pin 19 carried by the L shaped bracket 20 which is secured to the movable member 21, by means of the screw 22. The member l21 preferably is formed of moulded insulating material such as bakelite or the like. Y The insulating movable member 21 is mounted upon the pivot pin 23 carried in the spaced apart arms of the yoke 24 which in turn is secured to the switch operating shaft 13 by means ofthe screw 25. Two springs 26 and 27 loosely encircle the switch operating shaft 13 on either side of the yoke 24. These springs serve not only as spacers between the yoke 24 and the sides of the casing 10 to prevent axial displacement of the switch operating shaft 23, but also function to bias the movable member 21 carrying the bridging contact 17 for movement in one direction, namely,"in a counter-clockwise` direction about the. shaft 13 as shown in Figs. 3 to 6. One of the projecting ends of each of the springs 26 and 27 is arranged to engage with the shoulders 28 formed on either side'of the insulating movable member 21. In this way the biasing springs also operate to yieldingly ymaintain the insulating member `21 and the bridging contact 17 in a predetermined spaced and angular relation lwith the yoke 24 and the switch shaft 13. As will be pointed out more fully hereinafter, this manner of pivotally mounting the bridging contactI .17 permits both circumferential and radial movement thereof so as tokproduce a wiping action when the bridging contact 17 engages with the cooperating fixed'contact 18, when operating both as a normally closed and a normally open switch.

ln accordance with the present invention the fixed contacts 18 are arranged to be mounted within the casing 10 in two different circuit controlling relations with the bridging contact 17, one of these relations resulting in a normally closed switch and *the other relation resulting in a normally open switch. This is accomplished by mounting the fixed contactsV 18 in spaced apart relation upon one side of the block 30, preferably formed of moulded insulating material such 'as bakelite or the like, with the auxiliary terminal plates 31 on the opposite side of the insulating block. Each of the contacts 18 is electrically connected with the corresponding one of the terminal plates 31 by the screws 32 which pass through suitable holes in the block 30 and also serves to mechanically secure both the contact andthe terminal plate in position. The'bloek 30 is provided with a boss 33 extending between the fixed contact 18 so as to maintain the same in spaced alignment and at the same time provide an insulating barrier between the contacts. On the opposite side, the 'boss 34 similarly serves as an insulating barrier to maintain the terminal plates 31 in fixed alignment.l The block 30 is provided with a hole extending through the bosses 33 and 34 preferably with each r end of the hole recessed so asto receive the head of the screw 35 by means of which the block 30 is securedl to the switch enclosing casing 10. The notched lrecesses 36 formed in the opposite sides of the block 3() extend between the fixed switch contacts 18 and the terminal plates 31 so as to provide the required insulation creepage surface therebetween.

The whole design and arrangement of the supporting block 30 for the fixed switch contacts 18 is such that the block 30 may be assembled in the enclosing switch casing 10 with the boss 33 engaging the bottom of the casing as shown in Figs. 3 and 4 or with the boss 34 engaging the bottom of the casing as shown in Figs. 5 and 6. In the first case the` fixed contacts 18 are located in the path of movement of the bridging. contact 17 with the bridging contact biased out of engagement with the contacts 18. `In the second case the contacts 18 are located in the path of movement of the bridging contact 17 with the latter biased into engagement with the contacts 18. Thus it will be seen that in the first case a normally open switch is obtained while in' the second case a normally closed switch is obtained.

With the kblock and fixed contacts 18 mounted in the switch casing 10 to form a normally open switch as shown in Figs. 3

and 4 the projecting shoulder 37 formed on the block 30 serves as a `stop that limits the counter-clockwise movement of the contact 17 in accordance with its bias, thus maintaining the bridging Contact 17 a predetermined distance away from the cooperating fixed contacts 18. W'ith the actuating lever arm 14 carrying the roller 15 secured to the switch operating shaft 13 in a suitable position to be engaged by some movable member 38 as indicated in dotted lines in Fig. ,1, movement of the member 38 in the direction of either of the arrows into engagement with the roller 15 will rotate the switch operating shaft 13 in a clockwise direction. The clockwise movement of the operating shaft 13 is transmitted to the bridging contact 17 through the bracket 24 and the insulating member 21 pivotally mounted thereupon so as to operate the bridging contact 17 against its bias into circuit closing engagement with the fixed contacts 18. Vhen the bridging contact 17 engages with the fixed contacts 18, the springs' 26 and 27 yield to permit pivotal movement of the block 21 on the pin 23 so as to produce a wiping action between the bridging contact 17 and the stationary contacts 18. As shown in Fig. 4 the end of the spring 26 engages with only the nearest one of the shoulders 28 on the insulating member 21 as the insulating member 21 pivots uponl the pin 23 when the clockwise movement of the shaft 13 and the bracket 24 is continued after the initial engagement of the contacts. It may be noted that the amount of clockwise movement of the shaft 13 is limited by the engagement of the sloping side of the member 21 with the bottom of the switch enclosing casingUlO. Upon continued or return movement of the actuating member 38, the bridging member 17 is carried in accordance with its bias out ,of engagement with the fixed contacts 18 and returns into engagement with the shoulder stop 37, leaving the switch in the normally open position.

When the block 30 and the contacts 18 are reversed and assembled in the enclosing casing 10 to form a normally closed switch as shown in Figs. 5 and 6, the bridging contact 17 is biased into circuit closing engagement with the fixed contacts 18. The fixed contacts 18 then serve as stops to limit the counter-clockwise movement` ofv the bridging contact 17 in accordance with its bias. In this case the end of the biasing spring 26 engages with the far shoulder 28 on the insulating member 21 so as to permit ywiping movement of the bridging contact 17 on the fixed contacts 18 thereby insuring that the Contact surfaces are maintained in good condition. Upon movement of the actuating member 38 into engagement with the roller 15, as previously described, the resultytact 17 upon the insulating member 21 and the pivotal mounting of the latter upon the bracket 24, together with operation of the p end of the biasing springs upon the shoulders 28 formed on the insulating member 21, insures at all times a self-aligning wiping engagement of the bridging contact with the fixed contacts as previously pointed out. Moreover in case one edge of the bridging contact 17 should become worn or damaged by arcing during service the contact may be reversed upon loosening the screw 22 and disengagement with the pin 19 so as to present` the other edge for bridging engagement with the fixed contacts 18.

While I have described the preferred embodiment of the present invention, it will be evident that various changes and modifications may be made in the improved form of convertible switch without departing from the true spirit and scope of the invention.

lfVhat I claim as new and desire to secure by Letters Patent of the United States, is

1. A convertible switch comprising a support, a plurality of cooperating switch elements, one movably mounted on the support and biased for movement in one direction, and means associated with another of said switch elements for iXedly mounting the same on said support in two different cooperating circuit controlling relations with said biased movable switch element, one of said cooperating relations resulting in a normally closed switch and the other of said cooperating relations resulting in a normally open switch.

2. A convertible switch comprising a support, a movable switch contact mounted on the support and biased for movement in one directionV and' operable in the other direction, and a cooperating lswitch contact having means associated therewith for mounting the same on said support with said movable switch contact biased either into or out of engagement therewith to thereby form either a normally closed or a normally opened switch.

3. A convertible' switch comprising a support having a switch element pivotally mounted thereon and biased for movement in one direction about the pivotal support thereon, another switch element having means associated therewith for mounting the same on said support in two different positions in the path of movement of said pivotally mounted switch, one element of said posit-ions resulting in a normally closed switch and the other of said positions resulting in a normally open switch, and means for operat- 1ng said pivotally mounted switch against its las.

4.' A convertible switch comprising a support, a movable bridging contact movably mounted thereon and biased for movement 'in one direction and operable in the other direction, and a pair of spaced apart switch contacts having means associated therewith for mounting` the same on said support with the movable bridging contact biased into or out of wiping engagement therewith to thereby form either a normally closed or a normally opened switch.

5. A convertible switch comprising an enclosing casing, a rotatable operating shaft mounted in the casing and having a movable switch contact secured thereto within the casing and an operating member secured thereto without the casing and a contact cooperating with said movable contact and having means associated therewith for mounting the same in said casing in two different cooperating relations with said movable switch contact, one of said cooperating relations re-` sulting in a normally closed switch and another of said cooperating relations resulting in a normally openl switch.

6. A convertible switch comprising a casing having a switch operating shaft pivotally mounted therein, a bridging contact mounted on said shaft within the casing, a biasing spring connected between the casing and the bridging switch member for biasing the latter for movement in a predetermined direction, a pair of contacts mounted in spaced relation on a supporting block, means for mounting the supporting block with the contacts thereon in said casing with the spaced apart contacts in two different circuit controlling relations with said movable switch element, one relation resulting in a normally closed switch and the other relation resulting in a normally open switch, and means secured to the shaft outside the casing for operating said bridging contact against its bias.

7. A' convertible switch comprising a casing, a rotatable switch operating shaft mounted in the casing, a switch supporting member secured to the shaft within the cas ing, a bridging contact member mounted upon said member for movement relative to the switch shaft, a spring for biasing the bridging switch contact for movement in one direction, a pair of cooperating contacts for l the bridging member mounted in spaced rewiping engagement with the spaced apart contacts.

8. A convertible switch comprising a casing having a switch operating shaft pivotally mounted therein,` an arm secured to the shaft within the casing, an insulating member having a bridging contact loosely mounted thereon, said. member being movably mounted upon said arm to permit movement of the bridging contact in both a circumferential anda radial direction with respect to the opcratingshaft, a pair of fixed contacts cooperating with said bridging contact, said ixed contacts being mounted in spaced relation upon an insulating block, means for securing the block in said casing with the contacts thereon in thepath of movement of said bridging contact with the bridglng contact biased either into or out of wiping engagement with the pair of fixed contacts, and means secured to said switch operating shaft outside said casing for operating the bridging contact against its bias.

9. A convertible switch comprising acasing having a removable cover, a rotatable switch shaft mounted in the said casing, a yoke arm secured to the shaft within the casing, an insulating member pivotally mounted upon said yoke arm with `the axis of the pivotal mounting thereof substantially parallel to the switch operating shaft and having` spaced apart shoulders on either side of the axis of said pivotal mounting, a bridging switch contact loosely mounted on said insulating member, a spring surrounding said switch operating shaft and having one end engaging with the casing and the other end' engaging with the said shoulders on said insulating member for biasing the bridging contact member for movement in one direction and for maintaining the insulating memberf and the contact mounted thereon in a predetermined relatiorf with the said yoke arm, a pair of xed contacts cooperating with the said bridging Contact and mounted in spaced relation upon an insulating support, said support being adapted to be secured in said casing with the spaced apart fixed contacts in two different positionsin the path of movement of the bridging contact, said bridging contact being biased into circuit closing engagement with the fixed contact in one of said relations and biased out of circuit closing engagement with the fixed con- -tact in the other of said positions, and an operating lever adjustably secured-to the switch operating shaft outside the casing. for operating the bridging contact against its bias.

In witness whereof,- I have hereunto 'sett my hand this 30th day of J une, 1927.

GEORGE R. TOWNSEND. 

